Fireproof fiber product



atentd ay 24, 1932 RO GER 3. BROWN, OF. TEN,

NEW JERSEY, ASSIGNOR TO DANIEL MANSON LAND 2TB, OF MORRISVILLE, PENNSYLVANIA r amaoor FIBER. raonucr 1 No Drawing n,

My invention relates to fire-proofing for woody and fibrous materials, including artificial fiber products such as' thermal insula- 7 tion board and electrical insulation board of this character. I a

Many agents and methods for rendering .vegetable materialsuninfiammable have been proposed or used, includingsuch substances as ammonium sulphate, boric acid and some of its salts, calcium carbonate, etc, and certain organic chemicals, such as chlorinated naphthalene. These substances are objectionable in various ways, however: e. g.,

they are water soluble, so as to be readily dissolved out when the fiber is exposed to water; or the are hygroscopic, so'that materials treate always damp; or they add to the weight of the product unduly; ortheyare too expensive to be commercially 'practicable,as is especially the case with chlorinated naphthation on machinery that may be used inthe manufacture of the fire proofed product, or

on the means employed to hold or secure the finished product in use. In general, also, the use of such materials involves special processes of'impregnation, with pressure or vacuum, and subsequent drying,all of which tends to increase the cost. f

I have found that borates which are waterinsoluble and stable or inert toward water not hydrolyzing materially even in the presence of large amounts of 'waterare free from the drawbacks of the materials heretofore used. These include insoluble borates 'that are definitely alkaline in reaction, and

with them absorb water and are lene,or they have a strong corrosive ac- Applicationfiled September 10, 1930.- Serial No. 481,069.,

especially the alkaline earth borates, of magnesium, calcium, strontium, rand borium,as' well as the borates of copper and manganese. A calcium borate, and particularly calcium meta-borate, Oa(BO has been found to give-excellent results. All these borates can be introduced into natural. wood by known impregnation methods. In addition, they can be incorporate in arti- Jicial fiber board very readily and inexpensively, without the difiiculties of impregnation processes. Not only does the borate render wood fiber fire-resistant, but it also greatly reduces the inflammability of asphalts, resins, gums, and the like which are used for waterproofing purposes.

Calcium meta-borate is distinctly alkaline in reaction, and non-corrosive; non-hygroscopic; uninflammable and fire-resistant, merely melting or softening to a rather stifi' plasticity at the temperature of a flame, relatively insoluble in water; so that it will not wash out offibrous material fire-proofed with it; and can be precipitated from solution in .a flocculent, non-crystalline, bulky form,

giving it increased covering power for the fibers with which it is associated, without material effect the product.

Calcium meta borate can be formed by the interaction of'a solution of a water-soluble calcium salt with a solution of a water-soluble meta-borate, using equivalent amounts of on the density and weight of 'the two solutions 'CaGl +2NaBO Ga(BO +2NaGl Sodium metaborate, NaBO is' readily formed from sodium tetra-borate, Na B O by the action of caustic soda in solutidn': Y

Or calcium meta-borate can be made from borax, caustic soda, and calcium chloride (for example) according'to the following consolidated equation In practice, fiber board ismade from fiber pulp, consisting of wood fiber mixed and suspendedin a large volume of water. The

pulp is brought into a layer of proper thick ness, which is partly freed'of its water and then dried, either with or without pressure. In making fire-proof board according to my preferred process, I include in the pulp, or add to it, calcium meta-borate, Ca (B09 as well as a waterproofing-agent or material, if it is desired that the final product be waw terproof as well as fireproof. As a Waterproofing agent may be used any substance or material having this property that can be incorporated with the pulp so as to be properly distributed in the fiber board, such as watersoluble rosin size, rosin-wax size, or wax size. Many such materials commonly known as waterproofing agents can be incorporated in fiber pulp to waterproof the board made therefrom. The .fireproofing and water-' proofing agents thus incorporatedwith the pulp are used in such quantity or form that when the water of the pulp is removed, a sufficient amount of the'materials in question will remain interspersed amongst the fibers 5 in the board. In other words, the interstices amon stthe interlaced fibers are charged or even lled with the waterproofing and fireproofing materials, which are combined or intermixed with ne another more or less uni formly, .and the fibers are in either case coated with these materials and cemented together by them.

In general, it is better not to form the calcium meta-borate in the pulp itself by reactions such as above indicated, on account of the 'conseqduent presenceof other salts in not in appreciable quantity,

the final pro such as sodium chloride, which is obJectiOnable because of its solubility in water, its

duces the calcium meta-borate separately, in a rather concentrated solution, and to sepa rate the precipitate from the mother liquor, which carries the sodium chloride or the like in solution, by centrifuging or thelike.

The thus purified precipitate maybe added to the pulp either mixed and suspended- .in a'small amount of water, in which the rosin size or the like may be dissolved, 'or in its dry, owdery state, and thoroughly mixed in. ith rosin size for waterproofing, the following formula may be'used Lbs Rosin I size (boneedrybasis' Calcium meta-borate; Ca( 0 .3.. Water, previously saturated with This gives about 5% by weight of the proofing ingredient in the finished board.

' However, wide variation of this is permissi ble: i. e., as "little as 2% or less of the waterproofing ingredients in the board will produce a degree of fire resistance that may crystalline character, etc. On the contrary, I prefer toperform the reaction that pro Fiber 1,000'v cost; while for electrical insulation board to be used for switch bases, for example, as much as 15 to 20% of the borate (by weight) in the finished board may be necessary to enable. it to meet the underwriters requirements. To a degree, of course, the amount of fireproofing in redient required depends on the amount 0 highly inflammable =waterproofing ingredients present. The foregoing discussion presupposed not over 1 to 5% of such waterproofing (e. g., rosin size) in the board, which is generally ample.

After the calcium meta borate and the rosin size have been added to the pulp and thoroughly stirred in, the pulp is run into apressing mold (wet machine) with provisions for draining off the water, ,or otherwise formed into a raw pulp sheet freed of most of the Water. This raw sheet may then be pressed between heated drier plates, and thus converted into strong, coherent, waterproof. and fireproof board, consisting of the interlaced and compressed fibers andthe rosin (not resoluble in water), which cements the fibers together and more or less fills their interstices along with the calcium meta-borate. The insoluble particles of the metal-borate are dispersed in the rosin and embedded therein, besides clinging to the fiber particles as a coating. i

Wood has'heretofore been fire-proofed by .secondary impregnation with various substances, and it has been proposed to treat fiber aboard in the same way. Such impregnation, however, is subject to serious practical drawbacks:. I J

(1) Only liquids or reagents in solution can be introduced into the pores of the material in this way. Water-soluble reagents,

however, are easily washed or soaked out of the board.'

(2) To impregnate a board with an insoluble material, a two-step process is necessary: i. e., the board must first be impregnated with a solution of one reagent, and then with a solution of another reagent, which will react with the first to precipitate the desired insoluble material in the pores of theboard (3) The pores can never be completely filled with any solid introduced in solution;-

- whether by a one-stage or. two-stage process,

calcium metalomte about-nu s1nce the solvent water has to be drlven out.

pores are alrea' y; filled or clogged with the waterproof material.

All of these difiiculties and dlsadvantages of'secondary impregnation are overcome by 3 incor crating the fireproofing and waterproo g agents or materials in the pulp, as

described above; indeed, no special operation whatever is really required, slnce the pul is always thoroughly stirred or agitatedbe ore formation into a sheet, as a matter of ordina manufacturing practice.

-- aving thus described my invention, I

claim:

1. Wood fireproofed with a water-insoluble nonhydrolyzing borate interspersed amongst its fibers.

2. Fiber board comprising interlaced fibers having their interstices charged with a water-proofin material, and particles of a water-insolub e nonhydrolyzing borate embedded therein.

3. Wood fireproofed with calcium metaborate interspersed amongst its fibers.

0 4. Fiber board containing from 2% to of calcium meta-borate interspersed amongst its fibers.

In testimony whereof, I have .hereunto siined my name at Trenton, New Jersey, this 25 4t day of September, 1930.

ROGER B. BROWN. 

